Mid -Late 19th Century French Diamond Drop Necklace, in Antique Box

Possibly French with French markings to the tongue 
Dating from Mid-Late 19th Century 
Incredibly ornate Diamond Drop necklace
Detachable drop portion
Sliding hook
Converts into a Rivière or a bracelet
Silver set Diamonds with exquisite floral detail to the reverse in 14-15k Yellow Gold
Combined necklace length 39cm length: 15 3/4inches. 
Bracelet portion 7inches:18cm 
Diamond drop 27mm:1inch
Total Diamond weight approx 3.8cts  in Rose cut Diamonds 
Weight 27.6g
With fitted box from Harvey & Gore